A week ago, a plumber replaced a failing gate valve with a new ball valve on 3/4 inch copper pipe. It's my main water shutoff for the house. The day after the installation and for the following four or five days, I noticed a drop of water would form every several hours on the valve at the "seam" on the body of the valve (see attached picture - look near the center of the picture at the horizontal seam on the valve). The water does not seem to be coming from any of the obvious openings like near where the handle gets connected or where it was soldered. For the past couple days, I have not seen any more water leaking as described above. I was told by a representative of Webstone, the manufacturer of the valve, and someone else who works in the plumbing section of a local hardware store, that the leak likely occurred because of over heating during the soldering. I have a 30-day warranty with the plumber. Should I have the plumber come back and replace it with a new valve? (I'm concerned that, even though it has stopped for now, the leak may show up in the future and maybe get worse.) What do you think?

Need help here figuring out what this is on the side of my house under standing water. The green pipe in the middle is about 8". Got it pumped out with my little sump pump, but the ground water keeps filling it up. The reflection is me taking the pic. This thing sits on the side of my house where there's a low spot...could this be a drain the city put in for the standing water? We've had a lot of rain here in N.Texas the past week or so.